I have put myself on the beginners board because of the level of my questions?

I admit I am a point 'n shooter. However, on a recent vacation my brother lent me his new Nikon D40. Much fun. But based on recent Nikon product updates (I saw on dpreview) Nikon now has some Full Frame models selling for big bucks. What does Full Frame mean? Did the D40 (much cheaper than the new Nikons just out this week) have something less than full frame? Does this relate to the sensor size? If so, does this mean that full frame has a sensor as big as 35mm film transparency. I am confused?

Well, '35mm' cameras were called such because the film size for each image is 24x36mm and I guess someone decided 35mm sounded better than 36mm. So during the age of film we all got used to 35mm cameras. There were other film formats as well, ranging from the 110 pocket cameras and the 126 Kodaks all the way up to huge sheets of film for 4x5 (inches), 8x10 and even 11x14 cameras. Later APS film cameras also came into being and they offered certain advantages for everyday users.

Now focal length for a lens is directly related to film (or sensor) size. What we call a 'normal' lens means that the image on the film is roughly in proportion to what we see with our eye. If the image is magnified, we call it a telephoto lens. If the image appears to be stretched out, we call it a wide-angle lens. For 35mm lenses a 'normal' lens is considered to be 45-55 mm. For 120 film cameras, a 'normal' lens is around 80 mm.

Now when digital cameras came out we no longer had film, but we did have a rectangular sensor of specific dimensions. Most digital - 35mm type - cameras on the market today use a sensor that is smaller than the old 35mm film size. The Canon EOS-1D Mark III for example uses a sensor that is 18.7x28.7mm. A 'full-frame' camera in digital terms is one like the Canon 5D, 1Ds Mark II or the new Nikon that has a larger sensor that is the full 24x36mm in size.

Since people are used to considering focal lengths for lenses in 35 mm terms (a 50mm lens being 'normal'), the smaller sensors on most digital cameras introduce a crop factor of about 1.3 making the 50mm lens into a 65mm lens equivalent. Part of what we're dealing with is using archaic words to describe a new technology. This gets complicated because film is still around but more so because there are no longer just a few defined sensor sizes as there was with film.

As to why a 'full-frame' sensor is important, there are others on this list who can answer much better than I can, but basically with a digital sensor what matters is not only the total number of receptor sites on the sensor but the size of each receptor site as well. In theory at least one could pack 50 million receptors on a sensor the size of your baby fingernail, but such a sensor wouldn't be of much use.

Mike.

Logged

If your mind is attuned to beauty, you find beauty in everything.~ Jean Cooke ~

Originally (and most reasonably) "full frame" means a DSLR whose sensor is in the same format that the lenses used on it are designed for, as opposed to using a sensor smaller than the lens format and thus imposing a crop on the images produced by the lenses (as all DSLR's did before the Contax DSLR, followed by the Kodak 14/n and Canon 1Ds).

I call this "non-cropping".

For example- a Canon 1Ds with its 24x36mm sensor used with 35mm format lenses is full frame but a Canon 1D with these lenses has a 1.3x crop.- a 645 medium format camera and lenses with a 645 film back is full frame, but with a 36x48mm sensor in a digital back, it has a 1.2x crop.- a 4/3 format camera with 4/3 format lenses is also full frame, in this sense, but with 35mm lenses used through an adaptor, imposes a 2x crop.

Note: no-one ever said that medium format cameras are "more than full frame" due to having a larger than 24x36mm format, and I never heard anyone call APS film cameras "non full-frame" or "cropping", because they had lenses that matched their format.

The second common meaning is the 24x36mm format that was once common in the era of film cameras. This is a hang-over from the days when the only full frame (no-crop) digital cameras were in that format, before DX, EF-S and 4/3 lenses existed.

While we're on the topic, what exactly is 4/3 and why is Olympus championing this format? Is it merely an aspect ratio? What are the supposed advantages?[a href=\"index.php?act=findpost&pid=135184\"][{POST_SNAPBACK}][/a]

The idea behind the 4/3 format is that cameras and lenses will be smaller/lighter/cheaper.

For example, a popular telephoto zoom is 70-200. It is much cheaper to make a 35-100 mm f2.8 zoom for 4/3 than a equivalent 70-200 f 2.8 for a full-frame 35mm. "Cropped" sensors "seem" to loose out at wide angles, 16mm on full frame would need an equivalent of 8mm on 4/3, but since the 4/3 system is a completely new system the complexity of a 8mm lens is only the same as that of a 16mm lense as the mirror box is smaller (smaller sensor=smaller mirror=lens closer to sensor=less retrofocus design needed)

When the whole system is designed togeather the only two significant disadvantages of the smaller sensor are noise and view finder size/brightness.

I would guess that Olympus considered that with auto-focus getting better and better along with the live-view then the view finder becomes less critical and sensor noise seems to be getting better with each generation.

While we're on the topic, what exactly is 4/3 and why is Olympus championing this format? Is it merely an aspect ratio? What are the supposed advantages?[a href=\"index.php?act=findpost&pid=135184\"][{POST_SNAPBACK}][/a]

4/3 is a format of roughly 13x17.3mm, with the obscure name 4/3" coming from the weird jargon of video formats, where it referred to a sensor of total size 13.5x18mm. (The actual image size is smaller since as with all sensors, some pixels around the edge are not used as part of the output image). It also happens to have a 4:3 aspect ratio, as all the traditional video formats did.

It is the format adopted by Olympus (and Panasonic) for DLSR's aimed at roughly the same market as Canon's EF (now 14.8x22.2mm: it has got slightly smaller over the years!), Nikon's DX (about 15.8x23.6mm), and the formats used by Fuji, Pentax and Sony (all the same as Nikon's DX).

I can only guess as to why Olympus chose this format while other SLR makers chose slightly larger ones, and my guess is that the others were interested in a good degree of backward compatibility with their existing lenses for 35mm film cameras, at least during the transition while new lenses in the new formats (EF-S, DX, etc.) were added, but Olympus had little use for such backward compatibility, since it had no auto-focus 35mm film lens system. It had only a rather old fashioned, manual focus, all mechanically coupled lens mount system, of little interest to most DSLR buyers.

So Olympus decided to start from scratch with a new format smaller than 35mm (like everyone else) but also a completely new lens mount designed for that format (rather than reusing an "oversized" 35mm format lens mount like everyone else) and a completely new lens system. Since the format size was chosen with no regard for backward compatibility, it is rather natural that it ended up a bit different from, and smaller than, the EF-S and DX choices: backward compatibility probably pulled the EF-S and DX formats up closer to the 24x36mm of 35mm. Nikon might have had a goal of doing everything with DX format, before going with 24x36mm for one high end model, and such a goal would have lead to choosing a larger format than needed only for the DSLR mainstream.

Olympus has I think indicated a goal of matching or exceeding the technical quality of 35mm film with the smallest feasible lenses and cameras, helped by changes like having the lens mount closer to the sensor than was needed with 35mm film SLR's which allowing smaller, lighter bodies.

For the size and weigh advantages, look at the E-410 (435g, including battery) and its kit lenses, the 14-42/3.5-5.6 (190g) and 40-150/4-5.6 (220g). Still bigger than most digital cameras (since most are fixed-lens digicams in far smaller formats) but smaller and lighter than other DSLRs and lenses covering the same FOV ranges.